Introduction: How to Add a USB Fingerprint Scanner Internally to Laptop

I had a Dell Mini-9 that i installed Mac OS X onto and in the process saw other users adding an internal GPS receiver. This got me thinking, could I add a fingerprint scanner into it. The users of http://www.mydellmini.com were instrumental in the initial setup as one of the user found out where and how to add internal usb solder points. With this information I decided I had enough to tackle the project.

For this project you will need to have good soldering skills as there are some small points to solder to.

Tools needed:
Soldering iron and solder
Jeweler's screwdrivers
small files
Dremel
Dell Mini-9 (or any laptop worthy of modifying)
USB Fingerprint scanner
USB hub which you will dismantle as well
Double sided .001" thick Kapton Tape


LOTS OF PATIENCE as you will be ding some small soldering and drilling and filing away plastic from the palm rest and this can not be undone once it has been started.

This is my mod, I orginally posted it to the my dell mini forums and thought it would be good to have it here for more people to see and get ideas for their own. This has been seen on many other sites, doing a search on google for "dell mini-9 fingerprint scanner" brings up on lots of tech pages.

If you are ready to tackle this fun project let begin!

Step 1: Disassembly of the USB Hub

First we need to take the USB hub completely apart so that the circuit board is exposed and you have some length of wire still attached to the circuit board. 

Photo 1 shows the USB hub in its original case. (This photo is not mine as i was too anxious to get the project started)

Photo2: Remove the 6 screws holding the case together

Photo 3: Bottom cover comes off easily

Photo 4: Partially remove the top cover as to not rip off the wires from the circuit board, once it is apart far enough go ahead and cut the wires leaving enough that you know what color is what solder point

Photo 5: case is off the circuit board

Step 2: Lets Have a Look at the Circuit Board

Once you have the circuit board alone I went and made a drawing of each set of wires so I can later look an solder the wires up correctly to the fingerprint scanner. It is very important to make sure the wires are correct otherwise you risk frying the attached devise by wiring the positive to the negative or to one of the data points.

Once you have the layout of the wires I used the instructions here to wire the hub interantlly so it wont use one. I want to give a big thank you to the user that posted that as it was very helpful for this project, and future potential USB add-on's.

Once you have the hub installed we can continue on to the fingerprint modification.

Step 3: Disassembly of the Fingerprint Scanner

Lets take a look at the scanner I used. When I received this i was skeptical that it would not fit because of the size and weight of the device. I decided to dive in and see what it looked like inside, as that was the whole reason I bought the scanner and did everything to this point.

In the first four photos you can see the size of the device and why i was skeptical it would work. And on the fourth photo the weights they add so it would not slide when used.

As there are no screws holding the two parts together I used a small flat head screwdriver to pry the two pieces apart. I was not worried about snapping the plastic as it was no longer going to be used, but was cautious not to cause any damage to the internal card with the screwdriver.

Step 4: A Further Look at the Scanner

Now that we have the scanner apart, lets look at it more. As you can see, the actual circuit board is very small and thin, Perfect for installing inside the case.

DO NOT CUT THE WIRES YET, you will use these to solder to the USB hub installed earlier. I do suggest cutting the outside  sheath off as it is bulky and makes it difficult to run the cable around. I left mine on but would have removed it first if I were to do it over again.

The other card is my Runcore SSD for a size comparison

Step 5: Now for the Fun Part

This is where you will need lots of patience so you don't screw it up.
After disassembling the case per the MFG manuals I was looking where to place the scanner. I finally decided to place it under the right side palm rest as the only thing under it is the bluetooth receiver, and that is small enough to move.

The first photo shows the underside of the palm rest before grinding away the plastic posts. I did remove some foil in the area from the start because i knew it would cause problems with the circuit card if left there.

Using a Dremel with a cut-off wheel, SLOWLY grind away the posts until it is flat with the palm rest. To get through the inserts (metal bits for the screws) I ground a slot right thought the middle of the post so i can pull out the metal insert easily

Once you have ground it down it should look like the second photo

in the third photo I laid out the bluetooth and scanner to see a final fit before drilling through the case. As you can see it is a perfect fit between the bottom lip and the top lip, like it was meant to be there. 

Once you have the location of the board it is very important to start slowly. Drill three small holes using a sharp drill bit and going slowly. I used the drill bit in my fingers to i would not risk breaking the plastic and could feel it if bound up so I knew to stop. The hardest part of this is making sure the holes are in the center of the scanner bar. Once you have the holes drilled it will look like the fourth photo.

Now take a small flat file and start making the rectangle shape to fit the scanner's pickup. This should take longer that 30 minutes as to not take off too much. I kept checking the fit of the scanner every few minutes

The last step is to add a bevel to the top of the palm rest so that your finger can dip down and make easier contact to the reader bar. When i did this the file came off a couple times and scratched the top. Something that can be done to help stop this is to add a piece of masking tape just at the edge of where you want the edge of the bevel to meet the top as seen in the last photo

There are a few things that can be done to hold the scanner in place.

I prefer to use doublestick tape so that it can be removed if needed but still has a great holding power:  This is the tape I used between the palm rest and the circuit board for its properties with electronics, its thin, and has good holding and heat properties. Click here for (.001" Kapton®/Polyimide w/ Silicone)


Hope you enjoy this Intractable. Please post your comments

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